Guess the HP!

Post up a dyno sheet.
Not the graph, but a sheet with some data on it.

487hp from that combo is way low.

On the dyno here:
Flat top 446, untouched ootb RPM’s, xs282s cam, 1.5’s, SD/850, 1-7/8 x 3 headers……makes right at 500hp.

My first thought is…….it appears to be a vacuum secondary carb.
Maybe it’s not fully opening on the rear.
If the dyno shop has a decent DP on hand……. Try that.